Cross-section sample staining tool

ABSTRACT

An apparatus and method is disclosed for contacting samples with liquids. The apparatus includes a slotted support member positionable with respect to a container to allow a sample retained within the slot to be contacted by chemicals within the container. The slot in the support member is defined by opposing faces that are outwardly biasable and extend from a base. Preferably, three support members are spaced parallel to each other. The slots in the three support members are preferably aligned in parallel planes to allow larger wafer samples to be retained within the slots on more than one support member. A handle is preferably attached perpendicular to and bisecting each support member. Two bending rods are preferably disposed on opposite sides of the handle perpendicular to the support members. The bending bars are positioned to allow the support members to bent over the bars thereby outwardly biasing the opposing faces and opening the slots to receive the samples.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention generally relates to a sample preparation tool andmethods for using the tool. More particularly, the present inventionrelates to tools and methods for holding multiple semiconductor wafersamples that are to be stained with treatment chemicals prior tomicroanalysis, such as scanning electron microscopy, to allowsimultaneous sample preparation.

2. Description of the Invention Background

Integrated circuits are typically constructed by depositing a series ofindividual layers of predetermined materials on a wafer shapedsemiconductor substrate, or "wafer". The individual layers of theintegrated circuit are in turn produced by a series of manufacturingsteps. The performance characteristics of the circuits are dependentupon the ability to consistently produce the layers not only from waferto wafer, but from circuit to circuit on each wafer. The maintenance oftight manufacturing tolerances requires that strict quality controlprocedures be in place, including frequent sampling of the wafers forprocess characterization. Because of the numerous processing stepsinvolved in the production of semiconductor devices, a significantnumber of samples must be processed as part of a quality controlprogram. The layers of the wafer are characterized by surfacemorphology, chemical composition and crystal structure to providedetailed information of the quality of the layers and the processes usedto produce the layers. It is desirable to analyze the samples as closeto real time as possible to allow for an out of control process line tobe detected and corrected as soon as possible. Various microanalytictechniques are employed, such as optical, scanning electron (SEM) andtransmission electron (TEM) microscopy to determine the morphology ofthe layers. The characteristic dimensions of the layers are often a fewmicrons or less, which are well within the capabilities of the analytictools; however, the results of analyses performed on such short lengthscales can be highly affected by the preparation techniques used on thesamples. Variations in the preparation techniques can produce erroneousindications of product quality and process control problems. Inaddition, the amount of time necessary to prepare the samplesignificantly increases the time before an out of control process isdetected.

One such example of a technique that is afflicted with theaforementioned problems is in the preparation of samples for SEManalysis. In order to perform the SEM analysis, the wafers must besectioned to form samples and treated with staining chemicals, such asacids. The current practice in the semiconductor industry is to preparethe samples individually by first placing the sample in the stainingchemicals using tweezers. After a predetermined period of time, thesample is removed from the staining chemicals using the tweezers and thesample is rinsed to remove excess staining chemicals and then dried. Inmany SEM preparation techniques, the samples are exposed to multiplestaining chemicals to achieve the desired characteristics and the aboveprocedure must be performed for each staining procedure and for everysample. Obviously, this procedure is very time consuming and can alsoproduce scatter in the test results for a given sample lot due tovariations in many factors, such as exposure time and the varyingstrength of staining chemicals. As such, it would be highly desirable todevelop an apparatus and a method to stain wafer samples in a costeffective and timely manner that also tends to minimize the sample tosample variation introduced by the staining process to allow more timelyand accurate quality control data to be obtained.

The present invention is directed to an apparatus and method for whichovercomes, among others, the above-discussed problems so as to providean apparatus and a method to uniformly stain a sample lot in a timelymanner.

SUMMARY OF THE INVENTION

The above objects and others are accomplished by methods and apparatusesin accordance with the present invention. The apparatus includes atleast one slotted support member positionable with respect to acontainer to allow a sample retained within the slot to be contacted bychemicals within the container. A handle which may be attached to orintegral with the support member. The number of slots in the supportmember correspond to at least the number of wafer samples that are to beretained in the slots. Preferably, three support members are spacedparallel to each other and the slots in all three support members arealigned in parallel planes so that larger wafer samples can be seatedwithin the slots on more than one support member and the handle isattached perpendicular to and bisects each member. Also two bending rodsare disposed on opposite sides of the handle perpendicular to thesupport members for bending the support members to open the slots toreceive the wafer samples. It is also preferred that the apparatus beformed from a hard plastic material, such as fire resistantpolypropylene, or any other material that is sufficiently resistant tothe staining chemicals and that can be machined to incorporate slotssuitable to receive and retain the wafer samples without crushing thesamples.

In the practice of the invention, the wafer is sectioned into the numberof samples required by the testing procedure. The samples are insertedinto the slots in the support member, which retain the samples, whichcan then be simultaneously prepared for testing. The apparatus can beused during treatment and transportation of the samples in the varioussteps of sample preparation necessary prior to performing SEM on thesamples.

Accordingly, the present invention provides an apparatus and method forstaining semiconductor wafer samples that allows for more uniformstaining of the sample lot and significant shortening of the materialpreparation time for the analysis by allowing the simultaneouspreparation of multiple samples. These and other details, objects, andadvantages of the invention will become apparent as the followingdetailed description of a present preferred embodiment thereof proceeds.

BRIEF DESCRIPTION OF THE DRAWINGS

Preferred embodiments of the present invention will be described ingreater detail with reference to the accompanying drawings, wherein likemembers bear like reference numerals and wherein:

FIG. 1 is a bottom plan view of a preferred embodiment of the presentinvention showing the slots in the support members;

FIG. 2 is a front view of a preferred embodiment of the presentinvention in direction 2--2;

FIG. 3 is a side view of a preferred embodiment of the presentinvention;

FIG. 4 is a front view of a preferred embodiment of the presentinvention with the support members being bent over the bending rods toopen the slots to receive the wafer samples;

FIG. 5 is a back side view of a preferred embodiment of the presentinvention retaining six samples;

FIG. 6 is a top plan view of an alternative preferred embodimentsupported only by the handle on a container containing the stainingchemicals;

FIG. 7 is a side cross sectional view of a preferred embodiment of thepresent invention along line 7--7; and,

FIG. 8 is a top plan view of an alternative preferred embodiment inwhich the handle and a single support member are an integral elongatedmember which is seated on a container containing staining chemicals andsupporting six samples.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

The operation of the apparatus 10 will be described generally withreference to the drawings for the purpose of illustrating presentpreferred embodiments of the invention only and not for purposes oflimiting the same. The apparatus 10 of the present invention is used toretain multiple wafer samples 16 to allow for simultaneous preparationof the samples for various analysis techniques, such as SEM. Theapparatus 10 includes at least one slotted support member 12 and ahandle 14, which is attached to, or alternatively, integral with thesupport member 12. In one step of SEM processing, the apparatus 10 isused to expose multiple wafer samples 16 to staining chemicals 18contained in a container 20 having an open end 24 defined by a rim 22.

The support members 12 are preferably elongated members containing slots26, and having opposing ends 28 connected by a longitudinal axis and topand bottom surfaces, 30 and 32, respectively. The slots 26 are definedby opposing faces 34 and a base 35 in the bottom surface 32perpendicular to the longitudinal axis of the support member 12 and aresized to receive and retain the sample 16 by the clamping action of theopposing faces 34. The number of slots 26 in the support member 12corresponds to at least the number of samples to be retained in theslots. In a preferred embodiment, three support members 12 are used tosupport the samples 16. The longitudinal axes of the support members 12are aligned parallel to each other and the slots 26 in the supportmembers 12 are preferably aligned in parallel planes such that largersamples 16 can be retained in the slots 26 of all three support members12 simultaneously. A staggered arrangement of the slots 26 between thesupport members 12 may also be useful for retaining different sizedsamples. Also in a preferred embodiment, the support members 12 areidentical members as shown in FIG. 1, and have a length in the directionof the longitudinal axis that is greater than the dimensions of the rim22 of the container 20 so that the support members 12 will be seated onthe rim 22 when a portion of the samples 16 are placed into the stainingchemicals 18. Persons skilled in the art will appreciate that the numberof support members 12 and the number and arrangement of the slots 26 canbe modified to suit a specific application.

The handle 14 is also preferably an elongated member having top andbottom surfaces, 36 and 38. The handle 14 extends through the supportmembers 12 perpendicular to the longitudinal axes and the bottom surface38 is in a common plane with the bottom surfaces 32 of the supportmember 12. In a preferred embodiment, the handle 14 has an elongatedlength that is greater than the dimensions of the rim 22 of thecontainer 20 so that the handle 14 will be seated on the rim 22 when thesamples 16 are placed into the staining chemicals 18. The handle 14 canbe further provided with notches (not shown) in the bottom surface 38that can mate with the rim 22 of the container 20 to prevent sliding ofthe apparatus 10. The notches can also be provided in the bottomsurfaces 32 of the support member 12 to further prevent sliding of theapparatus 10 on the container 20.

In a preferred embodiment, two bending rods 40 are attached to the topsurface 30 of the support members 12 perpendicular to the longitudinalaxis of the support members 12. One bending rod 40 is disposed on eachside of the handle 14 and the bending rods 40 are preferably attacheddirectly opposite one of the slots 26 on the support members 12. A forcecan be applied to the opposing ends 28 of the support member 12 to bendthe support members 12 around the bending rods 40. The applied forceoutwardly biases the opposing faces 34 about the base 35 to separate theopposing faces 34 from a rest position, thereby opening the slots 26 toreceive the samples 16, as shown in FIG. 4. After the samples 16 havebeen inserted in the slots 26, the force is released from the supportmember 12 and the opposing faces 34 of the slots 26 attempt to return tothe rest position. However, the presence of the samples 16 prevents therelaxing of the opposing faces 34 back to the rest position and theopposing faces 34 exert opposing forces on the samples 16 that aresufficient to retain the samples 16 in the support member 12.

In a preferred embodiment, the support members 12, the handle 14 and thebending rods 40 are constructed from fire resistant polypropylene toprovide sufficient rigidity and durability to the apparatus 10. The fireresistant polypropylene has been found to be more resilient thanstandard polypropylene after repeated applications of the forcenecessary to open the slots 26 to insert and remove the samples 16 fromthe support members 12. Other materials having sufficient rigidity couldalso be used in the apparatus 10, such as Teflon,polytetrafluoroethylenes and other plastics, as well as metals; however,because the samples 16 are being held by the forces exerted by theopposing faces 34 of the support member 12, it is desirable to use amaterial for the support members 12 that is sufficiently rigid, butsofter than the samples 16 to minimize damage to the samples 16. Whilethe preferred embodiment has been described with the support member 12,the handle 14, and the bending rods 40 being separate componentsattached to each other, one skilled in the art will appreciate that allcomponents can be integrally formed as one piece or that variouscombinations of the components can be formed as single pieces.

Alternatively, as shown in FIGS. 6 and 7, the handle 14 can be attachedto the support members 12 such that the bottom surface 38 of the handle14 is not in a common plane with the bottom surface 32 of the supportmembers 12. In this embodiment, if the length of the support members 12is less than the dimensions of the rim 22, the support members 12 can belowered in the container 20, while the handle 14 is seated on the rim22, thereby allowing for a greater portion of the sample 40 to be placedinto the staining chemicals 18, as shown in FIG. 6. In this embodiment,as well as in other embodiments, additional handles 14 may be added toimpart additional stability to the apparatus 10 as it is seated upon thecontainer 20 or to provide flexibility in handling the apparatus 10 asmay be necessary depending upon the size of the apparatus 10.

In another embodiment shown in FIG. 8, the handle 14 and the supportmember 12 are integral and constitute a single elongated member 42containing slots 26 to receive and retain the samples 16. In thisembodiment, the samples 16 are supported perpendicular to the elongatedmember 42 and the elongated member 42 is seated upon the rim 22 when thesamples 16 are placed into the staining chemicals 18.

In the practice of the invention, a wafer is sectioned to produce thewafer samples 16. A force is applied to the bottom surface 32 at ends 28of the support members 12 to bend the support members 12 around thebending rods 40 to open the slots 26 to receive the wafer samples 16, asin FIG. 4. The wafer samples 16 are inserted into the slots 26 and theforce is released from the opposing ends 28. The opposing forces exertedon the samples 16 by the opposing faces 34 clamps the samples 16 in thesupport members 12, as shown in FIG. 5. The clamped samples 16 have aretained portion 44 and a free portion 46. In practice, the portion thatis to be the site to undergo SEM analysis should be the free portion 46,so as to reduce the possibility of damage to the analysis site. Theapparatus 10 is then positioned with the handle 14 seated on thecontainer 20, as generally illustrated in FIG. 6, such that the freeportion 46 of the samples 16 extends into the staining chemicals 18. Thesamples 16 are exposed to the staining chemicals 18 for a predeterminedperiod of time after which the samples are removed from the stainingchemicals 18. The samples 16 can then be rinsed to remove the excessstaining chemicals 18 and dried. The apparatus 10 can then be used toexpose the samples 16 to additional treatment chemicals and the aboveoutlined procedure can be repeated, if necessary. Following the finalstaining procedure, a force is again applied to the bottom surface 32 atopposing ends 28 of the support member 12 to bend the support members 12around the bending rods 40 to open the slots 26 and the samples 16 canbe removed and other samples may be inserted into the slots 26.

Those of ordinary skill in the art will appreciate that the presentinvention provides significant advantages over the current practice ofindividually staining, rinsing and drying the samples. In particular,the subject invention not only allows a large number of samples to beprepared at one time, it also ensures that the samples are exposed tothe same chemicals solution for the same period of time. In addition,the subject invention provides the additional benefit of minimizing thehandling of the sample that also provides for a higher quality samplefor examination and less exposure of personnel to potentially hazardouspreparation chemicals. While the subject invention provides these andother advantages over prior art, it will be understood, however, thatvarious changes in the details, materials and arrangements of parts andsteps which have been herein described and illustrated in order toexplain the nature of the invention may be made by those skilled in theart within the principle and scope of the invention as expressed in theappended claims.

What is claimed is:
 1. An apparatus for contacting at least one samplewith staining chemicals comprising:a container having an open end and aninterior for retaining staining chemicals; at least one support membercontaining at least one slot having opposing faces outwardly biasableabout a base and configured to retain a sample therein, wherein said atleast one support member is positionable to contact the sample withstaining chemicals in said interior of said container; and, at least onebending bar attached to said at least one support member to allow saidopposing faces to become outwardly biased about said base when saidsupport member is bent around said at least one bending bar.
 2. Theapparatus of claim 1 wherein one of said at least one support memberincludes an integral handle.
 3. The apparatus of claim 2 wherein:saidopen end is defined by a rim; and, said handle is seatable upon saidrim.
 4. The apparatus of claim 1 wherein said at least one supportmember comprises a plurality of support members.
 5. The apparatus ofclaim 4 wherein:said open end is defined by a rim; and, said pluralityof support members are seatable upon said rim.
 6. The apparatus of claim1, further comprising a handle attached to said at least one supportmember.
 7. The apparatus of claim 1, further comprising a handleattached to said at least one support member, wherein said handle isseatable upon said container with said at least one support memberdisposed within said interior of said container.
 8. The apparatus ofclaim 1, further comprising a handle attached substantiallyperpendicular to said at least one support member opposite to said atleast one slot.
 9. The apparatus of claim 8, wherein said at least onesupport member include a plurality of substantially parallel spacedsupport members containing a plurality of slots substantially parallelto said handle.
 10. The apparatus of claim 1, wherein said at least onebending bar includes a plurality of bending bars.
 11. The apparatus ofclaim 1, wherein said at least one bending bar includes a twosubstantially parallel spaced bending bars attached to said at least onesupport member parallel to and opposite said at least one slot.
 12. Theapparatus of claim 11, further comprising a handle attached to said atleast one support member substantially parallel to and between said twobending bars.
 13. The apparatus of claim 12, wherein:said at least onesupport member include a plurality of substantially parallel spacedsupport members containing a plurality of slots parallel to said handle.14. The apparatus of claim 1, wherein:said open end is defined by a rim;and, said at least one support member is seatable upon said rim.
 15. Theapparatus of claim 1, wherein said at least one support member includesa plurality of substantially parallel spaced support members containinga plurality of substantially parallel slots.
 16. The apparatus of claim1, wherein said at least one support member includes a plurality ofsubstantially parallel spaced support members containing a plurality ofsubstantially parallel slots that are substantially perpendicular tosaid plurality of said support members.
 17. The apparatus of claim 1,wherein said at least one support member is comprised of a materialselected from the group consisting of polypropylenes,polytetrafluoroethylenes, metals, and combinations thereof.
 18. Theapparatus of claim 1, wherein said at least one support member iscomprised of a fire resistant polypropylene.